This invention relates generally to processes for preparing parfried and frozen potato strips such as French fries. More specifically, this invention relates to an improved process and the resultant prepared potato strips which have a relatively low moisture content and are thus adapted for reconstitution or finish preparation in an oven, or alternately for rapid finish fry preparation, with a highly desirable combination of taste, appearance and textural characteristics. In accordance with one important aspect of the invention, the prepared potato strips are resistant to the development of so-called off-flavors during frozen storage prior to finish preparation.
Parfried and frozen potato strips, commonly referred to as French fries, are widely available in the foods industry. These potato products are conventionally prepared by cutting whole potatoes into elongated strips of a desired size and shape, and then partially cooking the potato strips by blanching in hot water or steam. Thereafter, the potato strips are partially fried, or parfried, in hot cooking oil, followed by freezing for packaging, shipping and/or storage. Prior to consumption, the parfried and frozen potato strips are reconstituted or finish prepared typically by finish frying in hot oil. French fried potato strips of this type are utilized extensively in restaurant and food service operations, and particularly in so-called fast food restaurants wherein it is desirable to produce a finish cooked product with a substantially optimized set of quality characteristics and with a relatively short finish fry preparation time.
More specifically, one major objective of potato processors is to provide parfried and frozen potato strips which can be finish prepared with a combination of taste, color, odor, and textural attributes selected for optimum consumer palatibility. For example, it is highly desirable to provide parfried and frozen potato strips which, after finish preparation, exhibit a light and tender but crispy exterior surface of golden brown fried color encasing a soft and mealy interior which is neither too dry nor too soggy. Moreover, especially in a fast food restaurant environment, it is important to provide finish cooked potato strips which can consistently retain these desired sensory qualities for an extended holding period of at least several minutes before actual consumption. In the past, achieving these desirable product qualities on a consistent basis has generally required that the potato strips be finish prepared by frying in hot oil. In a fast food establishment, to avoid advance preparation of potato strips that might not be sold or served within a limited holding time of several minutes, a relatively short finish fry step is desired and is typically on the order of about 2-3.25 minutes for smaller so-called shoestring size cut strips and about 3-4 minutes for larger strips cut sizes.
In recent years, alternative finish preparation methods such as oven heating have been researched in an attempt to eliminate the need to finish fry potato strips at the restaurant or food service facility. In this regard, traditional finish fry preparation methods have required specialized or dedicated frying equipment which must be maintained in a clean and sanitary condition. Moreover, finish frying steps inherently require the food service facility to use and handle significant amounts of cooking oil, with its associated cost and increasingly complex issues of used oil disposal. Further, there is an increased demand among health conscious consumers for food products having a reduced oil or fat content, whereby there is a growing demand for potato strips which are not finish prepared by frying. While these factors all contribute to an increasing interest in potato strips which have been finish prepared by means other than frying, the final product served to the consumer must exhibit a substantially optimized set of taste, appearance and textural characteristics similar to a conventional finish fried product in order to achieve consumer acceptance.
Oven finish preparation of parfried and frozen potato strips has generally involved significant modifications to the parfry preparation steps in order to provide French fry strips suitable for oven reconstitution. Specifically, parfried and frozen potato strips intended for oven finishing are typically processed to a strip moisture content which is lower than the moisture content of conventional parfried and frozen strips intended for finish preparation by frying. For example, conventional frozen French fry strips suitable for finish frying are typically parfried to a moisture content in the range of about 60-70% by weight. When such potato strips intended for finish fry preparation are instead finish prepared by oven heating, the reconstituted French fry strips are undesirably limp and soggy unless subjected to an extended oven heating cycle in which case the strips become excessively dry and tough. Conversely, frozen French fry strips designed for finish preparation by oven heating are normally parfried to a lower moisture content in the range of about 35-55%, and more preferably in the range of about 40-53%, and most preferably about 44-50% by weight. This reduced moisture content may be obtained by subjecting the potato strips to at least two parfry steps with an intermediate chilling or freezing step, prior to final freezing. Such reduced moisture strips can be finish prepared in an air impingement oven, a convection oven, or a conventional oven yet retain a desirable crisp exterior encasing a soft and mealy interior. It has also been recognized that such reduced moisture strips can be finish prepared by frying with a rapid, significantly reduced finish fry preparation time. See, for example, U.S. Pat. No. 4,590,080.
Storage stability problems have been encountered, however, with relatively low moisture parfried and frozen potato strips such as those designed for finish preparation in an oven. In particular, over a relatively short frozen storage period of a few weeks prior to finish preparation, the potato strips tend to develop so-called off-flavor characteristics which are described as stale, warmed over, or cardboard. Such off-flavors can also be detected when the low moisture potato strips are finish prepared by rapid frying, although the degree of off-flavor development can be partially masked by the finish fry step.
As one attempt to address this off-flavor phenomena in low moisture potato strips, it has been proposed to reduce the temperature at which the potato strips are parfried during a second parfry step prior to final freezing. In this regard, it is believed that off-flavor development is linked to end products of browning reactions such as Strecker degradation, and that the development of off-flavors can be minimized or eliminated by controlling the presence of browning reaction components such as 2,5-dimethyl pyrazine. See, U.S. Pat. No. 6,001,411, wherein the level of 2,5-dimethyl pyrazine in low moisture parfried and frozen potato strips is maintained at or below about 0.6 ppm, and preferably less than about 0.4 ppm by reducing the temperature of the cooking oil during a second parfry step to a relatively low level less than 335xc2x0 F. and preferably within the range of about 290xc2x0 F. to about 310xc2x0 F. While this approach is believed to provide improvement with respect to reduced development of off-flavors during frozen storage, it inherently requires a significantly longer parfry time to achieve the target low strip moisture level and thereby also prolongs the production process. In this regard, minor increases in the production process time correlate with a significant and extremely undesirable increase in production cost.
The present invention relates specifically to an improved low moisture parfried and frozen French fried potato strip product and related preparation process, wherein development of off-flavors during frozen storage is substantially reduced or eliminated by regulating the quantity of reducing sugar on the exterior surfaces of the strips prior to parfrying. The present invention provides control of browning reactions during parfrying, without requiring the potato strips to be parfried at a reduced temperature for an extended period of time, whereby the potato strips can be parfried and frozen without extending or prolonging the production process. The level of reducing sugar on the exterior surfaces of the strips is regulated in relation to the parfry temperature to produce strips having a target color when finish prepared by oven heating or by rapid finish frying.
In accordance with the invention, parfried frozen potato strips and a related preparation process are provided, wherein the potato strips have a relatively low moisture content suitable for oven finish preparation or alternately for rapid finish fry preparation, and further wherein the strips exhibit improved storage stability without developing undesirable off-flavor characteristics. The potato strips are surface treated to apply reducing sugar in a controlled amount prior to parfrying, to control browning reactions during parfrying in hot oil. The quantity of sugar on the exterior surfaces of the strips is regulated in relation to the parfry oil temperature to achieve a target strip color within a range of about 58-67 Agtron scale, and more preferably about 60-65 Agtron scale, and most preferably about 62 Agtron scale, upon subsequent finish preparation. In the parfried and final frozen state, these potato strips have a target strip color within a range of about 68-79 Agtron scale, and more preferably about 70-77 Agtron scale, and most preferably about 72 Agtron scale. Moreover, in the parfried and frozen state, the potato strips are additionally characterized by a relatively low level, less than about 0.6 ppm, and more preferably less than about 0.4 ppm of 2,5-dimethyl pyrazine.
The potato strips are initially blanched and then surface treated to apply reducing sugar in a controlled amount prior to parfrying in hot oil and freezing. In one form, the surface treatment is a dextrose-containing dip or spray, whereas in another form the surface treatment is a sugar-containing starch-based batter coating. In either case, the quantity of reducing sugar added on the exterior surfaces of the strips is regulated in inverse function to the parfry oil temperature to achieve the target strip color in the parfried and final frozen state within a range of about 68-79 Agtron scale, and more preferably about 70-77 Agtron scale, and most preferably about 72 Agtron scale. After finish preparation in an oven or rapid finish fry preparation, these potato strips exhibit a target strip color of about 58-67 Agtron scale, and more preferably about 60-65 Agtron scale, and most preferably about 62 Agtron scale. In a preferred preparation process, the potato strips are subjected to first and second parfry steps in hot oil with an intermediate freeze step prior to final freezing, wherein the quantity of reducing sugar on the exterior surfaces of the strips is regulated in relation to the temperature of the second parfry step to achieve the target strip color.